linux-kernel - Re: [RFC PATCH V6 2/7] ovl: mark overlayfs inode dirty when it has upper

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Date:   Fri, 26 Nov 2021 21:06:10 +0800
From:   Chengguang Xu <cgxu519@...ernel.net>
To:     "Jan Kara" <jack@...e.cz>
Cc:     "miklos" <miklos@...redi.hu>, "amir73il" <amir73il@...il.com>,
        "linux-unionfs" <linux-unionfs@...r.kernel.org>,
        "linux-fsdevel" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel" <linux-kernel@...r.kernel.org>,
        "Chengguang Xu" <charliecgxu@...cent.com>,
        "ronyjin" <ronyjin@...cent.com>
Subject: Re: [RFC PATCH V6 2/7] ovl: mark overlayfs inode dirty when it has
 upper

 ---- 在 星期五, 2021-11-26 17:10:07 Jan Kara <jack@...e.cz> 撰写 ----
 > On Mon 22-11-21 11:00:33, Chengguang Xu wrote:
 > > From: Chengguang Xu <charliecgxu@...cent.com>
 > > 
 > > We simply mark overlayfs inode dirty when it has upper,
 > > it's much simpler than mark dirtiness on modification.
 > > 
 > > Signed-off-by: Chengguang Xu <charliecgxu@...cent.com>
 > > ---
 > >  fs/overlayfs/inode.c | 4 +++-
 > >  fs/overlayfs/util.c  | 1 +
 > >  2 files changed, 4 insertions(+), 1 deletion(-)
 > > 
 > > diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
 > > index 1f36158c7dbe..027ffc0a2539 100644
 > > --- a/fs/overlayfs/inode.c
 > > +++ b/fs/overlayfs/inode.c
 > > @@ -778,8 +778,10 @@ void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
 > >  {
 > >      struct inode *realinode;
 > >  
 > > -    if (oip->upperdentry)
 > > +    if (oip->upperdentry) {
 > >          OVL_I(inode)->__upperdentry = oip->upperdentry;
 > > +        mark_inode_dirty(inode);
 > > +    }
 > >      if (oip->lowerpath && oip->lowerpath->dentry)
 > >          OVL_I(inode)->lower = igrab(d_inode(oip->lowerpath->dentry));
 > >      if (oip->lowerdata)
 > 
 > Hum, does this get called only for inodes with upper inode existing? I
 > suppose we do not need to track inodes that were not copied up because they
 > cannot be dirty? I'm sorry, my knowledge of overlayfs is rather limited so
 > I may be missing something basic.
 > 

Well, as long as overly inode has upper it can be modified without copy-up,
so we need to track all overlay inodes which have upper inode.

Thanks,
Chengguang